The present invention relates to a hand-guided drilling machine or percussion drilling machine.
German patent document DE-A 43 05 965 discloses a drilling machine which is provided with an arresting device for non-rotatably arresting a drilling spindle relative to a housing of the hand power tool, so that a drill chuck which is screwed with the drilling spindle is released from the drilling spindle and/or a tool can be clamped in the drilling chuck without a key. The known drilling machine has the disadvantage that the spindle arresting is released manually by a push button pressure. This poses the difficulty for the user to hold with one hand the tool or the tool chuck and with the other hand the drilling machine, in addition to the release the spindle arresting. Moreover, the presence of a safety device is required, to prevent that the spindle arresting is released during rotation of the drilling spindle.
U.S. Pat. No. 5,016,501 discloses an accu-bar screwdriver, in which an arresting coupling is provided between an output shaft of a planetary transmission and a hexagonal screwing tool receptacle. It is designed so that the bar screwdriver can be used as a manual hand screwdriver. The hexagonal receptacle is neither removable from the output shaft, nor a torque can be maintained during a tool exchange.
Accordingly, it is an object of the present invention to provide a hand-guided drilling or percussion drilling machine, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a hand-guided drilling or percussion drilling machine in which the arresting coupling is arrested between the drilling spindle or an intermediate shaft connected with the drilling spindle and a machine housing or a component connected with it, and the arresting coupling during a torque transmission from the drive motor to the tool is opened automatically arid during the torque transmission toward the tool holder in an opposite direction is blocked automatically.
When the machine is designed in accordance with the present invention, it has the advantage that the tool in the tool receptacle can be clamped without problems without key or the tool chuck can be released without problems from the drilling spindle, since the drilling spindle is automatically arrested. A separate operator for the operation for arresting of the drilling spindle is not needed. In addition, the safety devices for preventing the rotary arresting with a rotatable drilling spindle are superfluous. The inventive drilling or percussion drilling machine therefore has a simpler construction and simpler operation.
It is especially advantageous when in accordance with the present invention, the arresting coupling is arranged on an intermediate shaft, since then the axial percussion movement of the drilling spindle does not provide a disturbing influence on the arresting of the drilling spindle.
It is also advantageous when in accordance with still a further embodiment of the present invention the intermediate shaft and the drilling spindle are coupled through a transmission connection with a negative transmission ratio, since then, in particular during screwing or unscrewing of the tool holder, opposite torque peaks are reduced.
The coupling claws of the arresting coupling on a toothed gear in accordance with another feature of the present invention provides for an especially simple construction of the arresting coupling. The toothed gear and the driver disc can be arranged on the same shaft so as to reduce components tolerances and to guarantee an especially reliable arresting.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.